1. Technical Field
The present disclosure relates to a starter incorporating an electromagnetic solenoid unit which is used in an idle stop system.
2. Related Art
Recently, an increasing number of vehicles are equipped with an idle stop system (hereinafter referred to as “ISS” for short) which automatically controls stop and restart of an engine for the purpose, for example, of reducing carbon dioxide and enhancing fuel efficiency.
Starters based on conventional art are not able to restart an engine in a period following idle stop until complete stop of the engine, i.e. during rotation by inertia of the engine. The “starters based on conventional art” refers to those starters which use a single solenoid switch (referred to as “non-ISS switch” here) to push a pinion toward the ring gear of an engine and to open/close a main contact for the connection/disconnection of electric current supplied to the motor.
On the other hand, another type of well-known starter include, as disclosed in a patent document JP-A-2011-144799, for example, a tandem solenoid switch (hereinafter referred to as “ISS switch”) which is able to restart an engine in response to a restart request of the driver when the engine rotating due to inertia.
Such an ISS switch includes a solenoid SL1 for pushing a pinion and a solenoid SL2 for opening/closing a main contact and is configured to independently control the activation of the solenoids SL1 and SL2. Specifically, the movement of the solenoid SL1 for pushing a pinion is controlled independent of the movement of the solenoid SL2 for opening/closing a main contact. Therefore, when the engine is rotating due to inertia, the pinion can be brought into engagement with the ring gear for the restart of the engine.
However, in the ISS switch based on conventional art, the solenoids SL1 and SL2 are independently activated, irrespective of their order of activation. Therefore, both of the solenoids SL1 and SL2 require to have a heat capacity that can tolerate continuous current supply equivalent to “rated actuation time+margin” of the starter. This raises a problem that the solenoids SL1 and SL2 will have a large size in order to ensure their heat resistance.
Further, since the solenoids SL1 and SL2 are both controlled by a vehicle-side ECU, two terminals (hereinafter referred to as “terminals-50”) are necessary for passing current to both of the solenoids SL1 and SL2. Specifically, since the terminal-50 for the solenoid SL1 and the terminal-50 for the solenoid SL2 are separately provided, the connector of the terminals-50 will have a large size. This not only leads to the difficulty of mounting the starter on a vehicle, but also to the increase of the cost incurred in the ISS because there is also a necessity of providing two systems of harness and starter relay for connection to the two terminals-50.
Further, in the ISS switch based on conventional art, the current value for holding the plunger of the solenoid SL1 is made larger than the corresponding current value in the non-ISS switch, in order to ensure pinion engagement performance which is equivalent to that of the non-ISS switch. Therefore, depending on the type of vehicles, the fuse capacity of each terminal-50 harness is required to be increased, or the diameter of a harness wire is required to be increased, and this raises a problem of increasing the cost incurred in the ISS.